Slide assemblies are widely used on different applications including office furniture, kitchen furniture and rack of server. The conventional slide assemblies often seen include two rails and three rails which are retractably cooperated with drawers. In some conditions of use, the users want to position the slide parts to be positioned at open status when they are pulled out and the positioning device for the slide parts are then developed. Taken the three-rail slide assembly as an example, it generally includes two positioning members to position the first and second rails, and the second and third rails. A manual release member is used to release the positioning device for the second and third rails, and the positioning status between the first and second rails is automatically released by retracting the third rail.
For the positioning device, especially for the third rail automatically releasing the positioning status between the first and second rails, the applicant has been filed many patent applications such as U.S. Pat. Nos. 6,585,335, 6,899,408, 6,997,611, 7,118,277, and 7,520,577. These are for reference in this case.